Contrast adjustment is an important feature in many products and applications that process media content. Contrast adjustment techniques aim to emphasize differences in the visual properties of an image to make objects in the image distinguishable from each other and their background.
Contrast adjustment techniques typically involve the application of a transformation function that maps input pixel values to output pixel values. The transformation function aims to generate desired characteristics for the output pixel values. Such desired output pixel characteristics are commonly expressed in the form of a histogram (also referred to as a target histogram).
A transformation function can be automatically determined from the histogram information of an input image and the histogram information of its corresponding transformed output image. Despite this, challenges exist in properly specifying a target histogram for a transformed output image such that a visually pleasurable output image can be expected.